I have a 1980 300SD Mercedes and I'm having problems with my speedometer. I've removed the Instrument panel and removed the cable and found that it was working. I drove the car around to find out that it was working. I then reinstalled the cable making sure the cable went into the housing and tightened the cable. Pushed the instrument back in and drove the car but the speedometer still didn't work. Can I replace the whole instrument panel? How do I solve this problem.